1. Field of the Invention
The present invention relates to a fingerprint verification method which compares a fingerprint to be examined with a stored reference fingerprint, and finds application, for example, as a security system which opens a door only for registered persons.
2. Description of the Related Art
According to the conventional fingerprint verification method for a security system, an image including the protuberant lines of a fingerprint is binarized and thinned so as to calculate a protuberant line pattern. Then branch points, end points and curvature are extracted from the above protuberant line pattern as the main characteristics of the fingerprint. Based on those characteristics, a comparison is performed between a master image (image of a reference fingerprint) and a sample image (image of a finger-print to be examined). Since the characteristics appear all over the fingerprint, it was preferable for the conventional fingerprint verification method to have a fingerprint which covered a wide area. Therefore, the image of the fingerprint had to be taken by rotating the finger which included not only the front part of the finger but also the sides of the finger.
The protuberant lines at the lower portion of the fingerprint, i.e., a joint part of a finger, are usually arranged in a horizontal direction; therefore, there are few characteristics. Furthermore, the image at the lower portion of the fingerprint is usually input incorrectly; therefore, it is ineffective data for fingerprint verification. Accordingly, when using such an image for fingerprint verification, accurate verification will be difficult to perform due to the vast volume of noise in the data. Also, when using data representing the lower part of the fingerprint, the volume of input data becomes so large that it becomes necessary to expand memory capacity.
Furthermore, when a whole fingerprint is used for fingerprint verification, it is difficult to impress the fingerprint to be examined; therefore, the time required for fingerprint verification is long.